Recombinant enterokinase light chain with affinity tag: Expression from Saccharomyces cerevisiae and its utilities in fusion protein technology

Enterokinase and recombinant enterokinase light chain (rEK(L)) have been us ed widely to cleave fusion proteins with the target sequence of (AsP)(4)-Ly s. In this work, we show that their utility as a site-specific cleavage age nt is compromised by sporadic cleavage at other sites, albeit at low levels . Further degradation of the fusion protein in cleavage reaction is due to an intrinsic broad specificity of the enzyme rather than to the presence of contaminating proteases. To offer facilitated purification from fermentati on broth and efficient removal of rEK(L) after cleavage reaction, thus mini mizing unwanted cleavage of target protein, histidine affinity tag was intr oduced into rEK(L). Utilizing the secretion enhancer peptide derived from t he human interleukin 1 beta, the recombinant EKL was expressed in Saccharom yces cerevisiae and efficiently secreted into culture medium. The C-termina l His-tagged EKL was purified in a single-step procedure on nickel affinity chromatography. It retained full enzymatic activity similar to that of EKL , whereas the N-terminal His-tagged EKL was neither efficiently purified no r had any enzymatic activity. After cleavage reaction of fusion protein, th e C-terminal His-tagged EKL was efficiently removed from the reaction mixtu re by a single passage through nickel-NTA spin column. The simple affinity tag renders rEK(L) extremely useful for purification, post-cleavage removal , recovery, and recycling and will broaden the utility and the versatility of the enterokinase for the production of recombinant proteins. (C) 2001 Jo hn Wiley & Sons, Inc.